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Complex carbohydrates in the dietary management of patients with glycogenosis caused by glucose-6-phosphatase deficiency.

Carbohydrates with digestion characteristics between those of lente uncooked starches and rapidly digestible oligosaccharides were administered in a dose of 1.5 g/kg body weight to five patients with glycogenosis from glucose-6-phosphatase deficiency. Postprandial duration of normoglycemia and concentrations of blood insulin and lactate were determined. Uncooked barley groats in water, or incorporated in a meal turned out to behave as lente carbohydrates. Uncooked couscous in water, couscous incorporated in a meal, and partially cooked macaroni given as a meal behaved as semilente carbohydrates as compared with uncooked cornstarch and glucose. The in vitro determination of the digestibility index along with the in vivo tolerance test enables us to choose and incorporate semilente carbohydrates in the day-time treatment of patients.

Adolescent↗

Muscle as a putative producer of acid alpha-glucosidase for glycogenosis type II gene therapy.

Glycogenosis type II (GSD II) is a lysosomal disorder affecting skeletal and cardiac muscle. In the infantile form of the disease, patients display cardiac impairment, which is fatal before 2 years of life. Patients with juvenile or adult forms can present diaphragm involvement leading to respiratory failure. The enzymatic defect in GSD II results from mutations in the acid alpha-glucosidase (GAA) gene, which encodes a 76 kDa protein involved in intralysosomal glycogen hydrolysis. We previously reported the use of an adenovirus vector expressing GAA (AdGAA) for the transduction of myoblasts and myotubes cultures from GSD II patients. Transduced cells secreted GAA in the medium, and GAA was internalized by receptor-mediated capture, allowing glycogen hydrolysis in untransduced cells. In this study, using a GSD II mouse model, we evaluated the feasibility of GSD II gene therapy using muscle as a secretary organ. Adenovirus vector encoding AdGAA was injected in the gastrocnemius of neonates. We detected a strong expression of GAA in the injected muscle, secretion into plasma, and uptake by peripheral skeletal muscle and the heart. Moreover, glycogen content was decreased in these tissues. Electron microscopy demonstrated the disappearance of destruction foci, normally present in untreated mice. We thus demonstrate for the first time that muscle can be considered as a safe and easily accessible organ for GSD II gene therapy.

Adenoviridae↗

X-linked liver glycogenosis: localization and isolation of a candidate gene.

X-linked phosphorylase kinase (PHK) deficiency causes X-linked liver glycogenosis (XLG) which is the most frequent liver glycogen storage disorder in man. Recently we assigned XLG to the Xp22 chromosomal region by linkage analysis in two families segregating XLG. In this study a further localization of XLG in Xp22 was performed by extending the number of Xp22 markers, by extension of the number of family members from the two families of our previous study and by linkage analysis in four additional XLG families. Two-point linkage analysis revealed lod scores of 4.60, 5.73, 5.28, 8.62 and 5.14 for linkage between XLG and the DNA markers pXUT23 and pSE3.2-L(DXS16), pD2(DXS43), pTS247-(DXS197) and pPA4B(DXS207), respectively, all at 0% recombination. Linkage heterogeneity was not observed in this set of families. Multipoint linkage analysis increased the lod score for linkage between XLG and Xp22 to 16.79 relative to DXS197/DXS207. The position of the XLG gene was confirmed by analysis of recombinational events locating the XLG gene between DXS85 and DXS41. The XLG gene could not be mapped more precisely in this chromosomal region of approximately 20cM because of the absence of recombinational events between the XLG gene and the Xp22 markers. As we have previously shown that the rabbit liver alpha subunit of PHK (PHKA2) hybridizes to human Xp22, we isolated a human PHKA2 cDNA from a human hepatoma lambda gt11 cDNA library. Fluorescent in situ hybridization mapped human PHKA2 to Xp22. As this physical mapping coincides with the genetic mapping of XLG by linkage analysis, PHKA2 most probably harbours the mutation(s) responsible for XLG.

Amino Acid Sequence↗

X-linked liver glycogenosis type II (XLG II) is caused by mutations in PHKA2, the gene encoding the liver alpha subunit of phosphorylase kinase.

X-linked liver glycogenosis type II (XLG II) is a recently described X-linked liver glycogen storage disease, mainly characterized by enlarged liver and growth retardation. These clinical symptoms are very similar to those of XLG I. In contrast to XLG I patients, however, XLG II patients do not show an in vitro enzymatic deficiency of phosphorylase kinase (PHK). Recently, mutations were identified in the gene encoding the liver alpha subunit of PHK (PHKA2) in XLG I patients. We have now studied the PHKA2 gene of four unrelated XLG II patients and identified four different mutations in the open reading frame, including a deletion of three nucleotides, an insertion of six nucleotides and two missense mutations. These results indicate that XLG II is due to mutations in PHKA2. In contrast to XLG I, XLG II is caused by mutations that lead to minor structural abnormalities in the primary structure of the liver alpha subunit of PHK. These mutations are found in a conserved RXX(X)T motif, resembling known phosphorylation sites that might be involved in the regulation of PHK. These findings might explain why the in vitro PHK enzymatic activity is not deficient in XLG II, whereas it is in XLG I.

Amino Acid Sequence↗

Mutation hotspots in the PHKA2 gene in X-linked liver glycogenosis due to phosphorylase kinase deficiency with atypical activity in blood cells (XLG2).

In five cases of X-linked liver glycogenosis subtype 2 (XLG2), we have identified mutations in the gene encoding the liver isoform of the phosphorylase kinase alpha subunit (PHKA2). XLG2 is a rare variant of X-linked phosphorylase kinase (Phk) deficiency of the liver. Whereas in the more common form of X-linked hepatic Phk deficiency, XLG1, the enzyme's activity is decreased both in liver and in blood cells, Phk activity in XLG2 is low in liver but normal or even enhanced in blood cells. Although missense, nonsense and splicesite mutations in the PHKA2 gene were recently identified in several cases of XLG1, no mutations have yet been described for XLG2 and a molecular explanation for the peculiar biochemical phenotype of XLG2 has been lacking. All mutations found in the present study result in non-conservative amino acid replacements of residues that are absolutely conserved between the alpha L, alpha M and beta subunits of Phk [H132P, H132Y, R186H (twice) and D299G]. Strikingly, in two pairs of cases the mutations affect the same codon. These results demonstrate that: (i) XLG2 is caused by mutations in PHKA2 and is therefore allelic with XLG1; and (ii) XLG2 mutations appear to cluster in limited sequence regions or even individual codons.

Amino Acid Sequence↗

A model of mRNA splicing in adult lysosomal storage disease (glycogenosis type II).

Glycogenosis type II is a recessively inherited disorder caused by mutations in the acid maltase (GAA) gene. Clinically, three different phenotypes are recognized: Infantile, juvenile and adult forms. A majority of compound heterozygous adult-onset patients carry a t-13g mutation in intron 1 associated with splicing out the first coding exon (exon 2). We have studied the mechanism of this mutation in a model system with wild-type and mutant minigenes expressed in a GAA deficient cell line. We have demonstrated that the mutation does not prevent normal splicing; low levels of correctly spliced mRNA are generated with the mutant construct. The data explain why the mutation is restricted to a milder, adult-onset phenotype. We also demonstrate that splicing out of exon 2 occurs with the wild-type construct, and thus represents alternative splicing which takes place in normal cells. Three splice variants (SV1, SV2 and SV3) are made with both the mutant and the wild-type constructs. Furthermore, as shown by RNAse protection assay, these mRNA variants are less abundant with the mutant construct. Thus, a major effect of the mutation appears to be a low splicing efficiency, since the total amount of all the transcripts generated from the mutant construct is reduced compared with the wild type. The removal of approximately 90% of the intron 1 (2.6 kb) sequence resulted in a dramatic increase in the levels of correctly spliced mRNA, indicating that the intron may contain a powerful transcriptional repressor.

Adult↗

Recurrent infection in glycogenosis type Ib: abnormal neutrophil motility related to impaired redistribution of adhesion sites.

Neutrophil function was investigated in a male child with glycogenosis type Ib who demonstrated susceptibility to staphylococcal infections and neutropenia. Random motility and directed migration of the patient's neutrophils in vitro were profoundly diminished. The patient's neutrophils stimulated in suspension with chemotactic factors (CFs) generated chemiluminescence that was comparable to or greater than that generated by neutrophils from controls, but the patient's neutrophils failed to assume a normal bipolar configuration in response to chemotactic stimuli. They also failed to demonstrate enhanced adherence after a single exposure to CFs or decreased adherence after sequential exposures to increasing concentrations of CFs. Unlike neutrophils from controls, the patient's neutrophils failed to redistribute surface adhesion sites from lamellipodia (anterior pole) to uropods (tail) after sequential CF stimuli. These findings indicate a functional link between CF-induced configurational changes and altered adhesiveness of neutrophils under conditions of directed locomotion and suggest that a redistribution of surface adhesion sites is related to the mechanism of neutrophil locomotion.

Adhesiveness↗

Concomitant branching enzyme and phosphorylase deficiencies. An unusual glycogenosis with extensive neuronal polyglucosan storage.

A baby girl was born hypotonic and was respirator-dependent until death at 43 days of age. A muscle biopsy revealed PAS-positive, diastase-resistant sarcoplasmic inclusions with a vaguely fibrillar structure by electron microscopy. Biochemical studies at autopsy disclosed complete absence of branching enzyme in skeletal muscle and heart, and a deficiency of phosphorylase activity in skeletal muscle with a modest reduction in myocardium. Storage material was present in glia and perikarya of neurons, increasing in amount in the rostrocaudal direction, involving most severely the motor neurons in the brain stem and spinal cord, dorsal root ganglia and myenteric plexi. Inclusions were also present in most organs, especially liver and skeletal muscle. Ultrastructurally, the inclusions ranged from granular aggregates of membrane-bound material concentrated in the region of Golgi apparatus to large filamentous bodies similar to polyglucosan bodies. This baby differs from other patients with infantile glycogenosis IV by the severity and onset of symptoms at birth, involvement of neuronal perikarya and widespread extraneural deposits. The combined deficiencies of branching enzyme and phosphorylase may have accounted for the unique clinical and neuropathological findings.

Central Nervous System↗

Changes in nervous tissue in bovine generalized glycogenosis type II.

Generalized Glycogenosis type II has been diagnosed in seven calves from a herd of cattle maintained at the Murdoch University Veterinary School Farm. The syndromes seen are equivalent to the infantile and childhood forms of the disease in humans. In the brain and spinal cord of the calves acid alpha-glucosidase activity was depressed and glycogen deposition was markedly increased. Swelling, vacuolation and glycogen deposition was present in neurones of the central and autonomic nervous systems and retina, in glia and in Schwann cells and fibroblasts within peripheral nerves. The distribution was similar to that seen in human cases. The glycogen was both membrane bound and free within the cytoplasm. Changes similar to those seen in axonal dystrophy were present and some nerve fibres showed Wallerian degeneration. Evidence of nerve cell destruction and nerve cell loss were not seen and the predominant clinical signs were related to muscle weakness.

Animals↗

Identification of heterozygotes for glycogenosis 2 (acid maltase deficiency).

In 21 obligate and 9 possible heterozygotes for acid maltase deficiency (AMD) (glycogenosis 2, Pompe's disease), different methods of identifying heterozygotes have been studied. Heterozygosity could not be demonstrated by physical examination, serum CPK assays, morphological examination of muscle biopsy (including light-microscopy, histochemistry and electron-microscopy), or by ultrastructural examination of a skin biopsy. Heterozygotes could be identified to a large, but still limited extent, by measuring the acid alpha-glucosidase activity in urine, cultivated fibroblasts, leucocytes, or skeletal muscle. Heterozygotes for the generalized from of AMD could not be distinguished from those for the muscular form. The limitations of heterozygote identification by means of enzyme assays are discussed, and some practical aspects for genetic counselling are mentioned.

Female↗

Prenatal diagnosis of glycogenosis type II (Pompe's disease) using chorionic villi biopsy.

Glycogenosis type II (Pompe's disease) has been diagnosed using cultured amniotic cells for several years. In this paper, we present three prenatal diagnoses based on chorionic villi biopsy in three families at risk for Pompe's disease juvenile form: a normal fetus that was diagnosed and confirmed by enzymatic assay on amniotic cells; two affected fetuses that were diagnosed and confirmed on post-abortion fetal tissues. In one case a residual acid alpha-glucosidase activity was found; we concluded that the residual activity was due to maternal contamination. Prenatal diagnosis of Pompe's disease is therefore possible using chorionic villi biopsy.

Biopsy↗

First trimester diagnosis of Pompe's disease (glycogenosis type II) with normal outcome: assay of acid alpha-glucosidase in chorionic villous biopsy using antibodies.

Prenatal diagnosis of glycogenosis type II was performed by direct assay of acid alpha-glucosidase (EC 3.2.1.20) in chorionic villous biopsy obtained by transcervical cannula aspiration from a pregnancy at risk in the 10th week of gestation. The exact value of the enzyme activity estimated by the use of antibody preparations for purified human liver acid alpha-glucosidase was in the heterozygous range, and so the homozygous enzyme deficiency could be excluded. The subsequent analysis of cells cultured from amniocentesis sampling in the 18th week of gestation resulted in a similar outcome. The study with antibodies showed that in 23 control chorionic villi obtained during gestational ages between 7-13 weeks, 1-15% of the total alpha-glucosidase activity at pH 4.0 were due to renal or neutral enzyme. This indicates that it may be important to employ antibodies for prenatal diagnosis using chorionic villous sampling. A healthy and unaffected boy was born. The biochemical values obtained from an umbilical blood specimen were in accordance with the results of the prenatal diagnosis.

Adult↗

Type IV glycogenosis - a study of two cases.

Liver biopsy materials of two siblings with type IV glycogenosis were studied by light and electron microscopy. Biochemical analysis was added using autopsy material in one of the two cases. Two kinds of polysaccharides were noted not only in the cardiac muscle, skeletal muscles, smooth muscles and reticuloendothelial cells, but also in the neutrophils and platelets. One was glycogen and the other was similar to amylopectin. Ultrastructurally, a large amount of fibrils, 60 A in width, glycogen rosettes and glycogen granules were detected in those cells. Branching glycosyltransferase deficiency was biochemically confirmed in one case examined.

Amylopectin↗

An autopsy case of type II glycogenosis.

An autopsy case of Type II glycogenosis was reported with detailed description of ultrastructural findings. In addition to two typical patterns of glycogen deposition, membrane-bound lysosomal glycogen and membrane-free cytoplasmic glycogen, we observed numerous vacuolar structures in liver cells and a large deposition of nomogeneous materials between fragmented myocardial fibrils. These findings were briefly discussed in this manuscript.

Autopsy↗

Type 1 glycogenosis with contracted kidneys and liver cell adenoma.

A 22-year-old man with type 1 glycogenosis died of renal and respiratory failure. Postmortem examination revealed deposition of glycogen in liver cells, a liver cell adenoma, bilateral contracted kidneys with scent glycogen deposition, and pulmonary edema. The development of liver cell adenoma was thought to be related to underlying metabolic disorder and contracted kidneys were considered to be the sequel of massive glycogen deposition in the renal tubular epithelium.

Adult↗

Immunological homogeneity of Lafora body, corpora amylacea, basophilic degeneration in heart, and intracytoplasmic inclusions of liver and heart in type IV glycogenosis.

Antisera against Lafora bodies were made in rabbits by subcutaneous injection of the myocardium from a patient died of Lafora disease. Using this antisera, immunohistochemistry revealed that corpora amylacea, the basophilic degeneration of myocardium and deposits of type IV glycogenosis contained the materials which were antigenically common to Lafora bodies.

Amyloid↗

Generalised glycogenosis in Brahman cattle.

Generalised glycogenosis was diagnosed in Brahman cattle on 4 Queensland properties on the basis of clinical observations and pathological and biochemical findings. The disease presented as a problem of ill-thrift and poor growth rate in calves which eventually showed nervous signs. Histologically there was vacuolation in the cells of the central nervous system, heart and muscular tissues. Biochemical assay of liver and blood mononuclear cells demonstrated a deficiency of alpha-glucosidase. Parents of affected calves had approximately half the alpha-glucosidase activity of that found in normal cattle.

Animals↗

Uncooked cornstarch--efficacy in type I glycogenosis.

Uncooked cornstarch (UCCS) loads in 14 patients with type 1 glycogenosis revealed that satisfactory glycaemia was achieved for a median of 4.25 hours (range 2.5 to 6). Length of glycaemia was related weakly to UCCS dose, but not to patient age or measures of metabolic control. Careful monitoring is required during UCCS treatment.

Adolescent↗